108 APPENDIX TO THE HISTOLOGICAL SECTION. 



3. Coprosive sublimate. HgCL 2 . A saturated solution in water 

 or normal saline. Fixation takes place rapidly in from five minutes to 

 two hours, the time being determined by the density and size of the 

 piece of tissue. As this reagent does not penetrate freely small pieces 

 only can be fixed. They must not exceed 6 mm thick, and these will 

 take two hours to fix. Thinner though wider pieces will take a shorter 

 time. 



Injection through the blood vessels" is the best method, complete penetra- 

 tion being secured in a few minutes. The parts must then be cut up rapidly 

 under running water. 



After-treatment with increasing strengths of alcohol tinted sherry 

 colour with iodine solution until discoloration ceases. The Iodine 

 helps to remove uncombined corrosive sublimate which would otherwise 

 form crystalline deposits and obscure the sections. Alcohol aids this. 

 removal, as corrosive is more soluble in it than in water (33 parts in 

 100 in alcohol, 25 in ether, 7 in water). 



4. Alcoholic copposive. 50 cc of 70 *>- c - alcohol, 50 cc of saturated' 

 solution of HgCl. 2 in 70 p - c - alcohol, 6 drops of HN0 3 . Only very 

 small pieces 4 mra thick can be fixed in this. Time required 1 to 4 

 hours. Then increasing strengths of alcohol. 



Note. Whilst the aqueous solution is one of the best general reagents the alcoholic 

 form is especially good for ganglia and glandular tissues such as liver, kidney and 

 salivary glands. Tissues stain well after corrosive treatment. 



5. Chpomie acid. Solutions from 0'2 up to 1 P- C - in water have been 

 used. This reagent is a bad penetrant, soon turns the tissues brittle, 

 and is now seldom used alone. It fixes well. The following mixtures 

 are used chiefly for epithelial and nuclear structures. 



6. Chpom-aeetie fluid (Flemming). Chromic acid 0'25 P- C -, acetic 

 acid O'l P-% in water, Very small pieces of tissue take about two days, 

 then increasing alcohols the weaker strengths being several times 

 renewed, until discoloration by the escaping chromic acid ceases. 



7. Chpomo-fopmic fluid (Rabl). To 200 cc of an aqueous 0'33 P- C - 

 solution of chromic acid add four or five drops of formic acid. Time 

 and after-treatment the same as 6. 



8. Chpomo-nitpic fluid (Perenyi). To 3 parts of 0'5 P- C - chromic 

 acid add 4 parts of 10P- C - nitric acid and lastly 3 parts of strong alcohol. 

 Time 4 to 8 hours, followed by the same after-treatment as 6. 



9. Chpomo-aeeto-osmie fluid (Flemming's fluid). A much used 

 cytological reagent. There are two formula?, the weak one is the more 

 useful. Chromic aeid 1 P- C - 25 parts, osmic acid 1 P- C - 10 parts, ascetic acid 



